Army Staff Sgt. Tim Kennedy, a Ranger and mixed martial artist, is excited about his chance at the Strikeforce middleweight championship. (Colin Kelly / Staff)

The sheet music on Army Staff Sgt. Tim Kennedy's piano right now is Rachmaninoff's second concerto. A hard-hitting masterpiece with an emotionally exhausting punch, it's a long, tough piece to tame, so it'll be there for a while.

While it may not be the "Rocky" theme, it's a fitting soundtrack for a man on his way to the fight of his life.

Kennedy will fight for the vacant Strikeforce mixed martial arts middleweight championship against Brazilian grappler Ronaldo Souza on Aug. 21 in Houston. The fight will air live on Showtime and the American Forces Network at 10 p.m. Eastern time.

Kennedy is no stranger to epic fights — in the cage or on the battlefield. A Special Forces sniper, Kennedy earned the Bronze Star during tours fighting Taliban and Iraqi insurgents. A devout Christian and resident of Austin, Texas, Kennedy now serves as an instructor for the Army National Guard's 19th Special Forces Group, headquartered in Utah with units spread across seven other states, including Texas.

Kennedy was a professional MMA fighter for three years before enlisting in 2004 and earning his SF and Ranger tabs.

He first started learning martial arts as a kid, about the time his mother forced him to sit down in front of a piano. "I grew to actually enjoy it. I still try to find time to practice," he says.

It's that same commitment that fuels three grueling workouts a day as he prepares for his bout against Souza. The regimen has paid off. His last four fights have ended quickly, with Kennedy walking away without a scratch.

"My last fight, I submitted the guy in 2˝ minutes and never got punched," he says.

But, he adds with deliberate pause, "I don't think this is going to be one of those fights."

On paper, the two look like an even match. Souza has an extra inch of height to Kennedy's 6-foot frame, and both will weigh in at 184 pounds. Souza also matches Kennedy's pro record of 12 wins and two losses (one of Souza's bouts also ended in a "no contest" after an illegal kick).

But while Kennedy is considered a powerful all-around fighter, Souza is known in his native Portuguese as "Jacaré" — the alligator — for good reason. He's widely hailed as one of the greatest jiujitsu artists alive.

"He is amazing. He's the most decorated grappler on the face of the planet," Kennedy says. "Jacaré can submit anyone from any position on the ground in a millisecond. Because he is so fluid and athletic, I'm going to have to get in there and be ugly and brutal, get in his face and break him down. It'll be fun to watch. It won't be fun to be a part of."